Thermoelasticity of segmented polyurethanes

Various diphenylmethane diisocyanate-containing polyurethanes whose soft blocks differ in polarity and crystallizability have been investigated using deformation and scanning calorimetry to ascertain the contribution of different types of intermolecular interaction to elasticity of polyurethane elastomers. The phase composition of polyurethanes being investigated and its dependence on mechanical action have been analyzed on the basis of scanning calorimetry data. By measuring the mechanical work and thermal effect during extension (λ=1–3.5) deformation dependences of internal energy changes and the ratio of energy and entropy changes have been determined as well as energy contributions have been calculated. The data obtained for different temperatures demonstrate that a decrease in the fraction of energy changes is largely due to hard block structurization in the course of re-building the network of hydrogen bonds during deformation.